Area Forecast Discussion
Issued by NWS Boston, MA

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000 FXUS61 KBOX 191914 AFDBOX Area Forecast Discussion National Weather Service Taunton MA 314 PM EDT Mon Mar 19 2018 .SYNOPSIS... Dry but unseasonably cold weather will continue through Tuesday. A coastal storm moves up from the Mid Atlantic coast Wednesday and then moves off to the east Thursday. High pressure brings drier weather Friday and early Saturday. && .NEAR TERM /THROUGH TONIGHT/... High pressure remains in control of our weather. Some increase in clouds, but otherwise rather quiet. Winds will gradually back through north to northeast and remain rather light. Expecting some radiational cooling, but not ideal. Min temperatures Tuesday morning expected to be about 10 degrees below normal. && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... Not expecting much significant weather Tuesday, as a high pressure remains nearby. As a low pressure develops off the coast of VA/NC and moves northeast, there is a low risk for some precipitation to reach the islands late in the day Tuesday. Expecting precipitation to overspread southern New England from SE to NW, mainly after midnight Wednesday. This timing is subject to change, and may hold off until after daybreak Wednesday to begin in earnest. Temperatures will remain below normal, setting the stage for some light snowfall Tuesday night. Snow will be more likely to accumulate at night, but any accumulations should be an inch or less through Tuesday night. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... Big Picture... Southern stream crosses the southern USA. One shortwave digs in over the southeast USA Tuesday night, turning the upper flow up the coast over New England. Closed low within this trough moves up the coast, crossing New England Wednesday night and the Maritimes Thursday. Northern stream trough drops down from Canada over the weekend. Model solutions are similar through Saturday morning with differences in detail after that. However, run-to-run differences continue and so forecast confidence is low-moderate. Details... Wednesday through Thursday... All models move a coastal low near the benchmark either Wednesday or Wednesday night. The GFS and GGEM are similar in timing this passage late afternoon/evening, while the ECMWF is slower with passage Wednesday night. This track is about 70 miles farther north than previous model runs, which would push precip farther north with a better chance to affect Southern New England Wednesday. Temperatures Wednesday will be borderline for accumulation, even after accounting for wet bulb processes. Even so, the scenario as presented shows potential for some snow accumulation, with a 4-5 inch bullseye in Southeast Mass with amounts diminishing toward the Northwest. Strong low level jet on the north side of this storm, with winds 50- 60 knots aloft. This should support northeast wind gusts 35-40 knots at the surface. A wind advisory may be needed for parts of Eastern Mass, especially the Cape and Islands. The forecast brings likely pops into Southern RI and Southeast Mass Wednesday with chance pops southeast of Fitchburg to Springfield MA. The low moves off to the northeast Thursday, and northwest winds bring drier air into our area that should aid in partial clearing. Friday-Saturday... Upper cyclonic flow lingers over New England Friday. Otherwise dry weather with seasonably cool temperatures. Sunday... Northern stream trough dives south from Canada Saturday night and sweeps over New England Sunday. This by itself may be enough for some flurries or light snow showers. Another shortwave moving through the southern stream passes south of us Sunday. Either source would be good for chance pops for rain or snow. Forecast confidence is low. && .AVIATION /19Z MONDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday Night/...High confidence. Tonight...VFR. Weaker NW winds. Tuesday...VFR through the day with increasing high and mid clouds. Winds N-NE. Tuesday Night...Mainly VFR, with local IFR possible. Windy with gusts to 35 kt. Slight chance SN towards the islands. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Wednesday through Friday/...Moderate Confidence. Wednesday: MVFR/IFR conditions possible. Strong winds with gusts to 45 kt, mostly in Eastern Mass. Chance SN. Wednesday Night: MVFR/IFR conditions possible. Strong winds with gusts to 50 kt, mostly in Eastern Mass. Chance SN. Thursday: Mainly VFR, with local MVFR possible. Strong winds with local gusts to 40 kt Thursday Night: VFR. Breezy. && .MARINE... Short Term /through Tuesday Night/...High confidence. Quiet winds and seas are expected through Tuesday. Winds increase and seas begin to build Tuesday night ahead of intensifying surface low pressure east of the Delmarva Peninsula. By daybreak Wednesday, NE wind gusts well into gale force will likely have worked their way into the outer southern coastal waters. Outlook /Wednesday through Friday/...Moderate Confidence. NE winds will ramp up Wednesday with gale force sustained winds or gale force gusts overtaking all waters by mid morning. Storm force gusts are likely late Wednesday morning through evening across the outer southern and eastern waters. Anomalously cold air will help with fairly efficient mixing through the boundary layer to bring the stronger wind gusts to the ocean surface. Have increased the SWANGFS wave height guidance field looks like a fairly good first cut and increased a relatively modest 5 to 10 percent. This results in waves of 15 to 20 feet forecast for east of Cape Ann, Stellwagen Bank, and Massachusetts Bay with a little over 20 feet projected for just east of Cape Cod and Nantucket. Winds back to the N Wednesday night and very gradually diminish overnight but still remaining as gale force through Thursday morning. Winds and seas gradually subside Thursday afternoon and night with seas projected to drop below 5 feet across the outer waters by Friday afternoon. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...Winter Storm Watch from Wednesday morning through Thursday morning for CTZ002>004. MA...Coastal Flood Watch late Wednesday night for MAZ019-022>024. Winter Storm Watch from Wednesday morning through Thursday morning for MAZ003>007-010>021-026. RI...Winter Storm Watch from Wednesday morning through Thursday morning for RIZ001>004-006-007. MARINE...Gale Watch from late Tuesday night through Wednesday evening for ANZ231>235-237-250-251-254>256. Small Craft Advisory until 2 AM EDT Tuesday for ANZ250-254. && $$ SYNOPSIS...WTB/Belk NEAR TERM...Belk SHORT TERM...Belk LONG TERM...WTB AVIATION...WTB/Belk MARINE...WTB/Belk is the U.S. government's official web portal to all federal, state and local government web resources and services.